/**
 * @param {character[]} s
 * @return {void} Do not return anything, modify s in-place instead.
 */
var reverseString = function(s) {
  for(let i = 0; i < Math.floor(s.length / 2); i++) {
    let temp = s[i];
    s[i] = s[s.length - i - 1];
    s[s.length - i - 1] = temp;
  }
  return s;
};


let s = ["h","e","l","l","o"];
console.log(reverseString(s));
s = ["H","a","n","n","a","h"];
console.log(reverseString(s))
